With brake pad assemblies of the type comprising a backplate with a friction lining at one side thereof and a dampening sheet at the other side thereof, the dampening sheet has the purpose of dampening unwanted vibrations, i.e. squealing noise, of the backplate during braking. In order to accomplish this purpose, the dampening sheet must be in contact with the backplate. With the usual design of disk brake assemblies, the braking force by which the backplate is pressed against the brake disk must be transmitted to the backplate via the dampening sheet. When braking occurs, the rotating brake disk seeks to take along with it the friction lining and the backplate, while the dampening sheet is held back by the element which applies the braking force to the brake pad. This creates very high shearing forces between the backplate and the dampening sheet.
While conventional connections between the backplate and the dampening sheet usually constitute bonding, additional measures need to be utilized to deal with the shearing forces taking into account that these additional measures must not deteriorate the ability of the dampening sheet to dampen the vibrations.
In previous brake pad assemblies, such as shown in Published European Patent Application EP 0 282 129, additional measures are provided to deal with such shearing forces between the backplate and the dampening sheet through projections of the dampening sheet in the form of knob-shaped or cup-like protuberances of the dampening sheet which are continuous and uninterrupted. The conical wall of the protuberance engages the limiting edge of a recess formed in the backplate. This arrangement causes considerable wear and, at the same time does not provide sufficient resistance against relative rotation between the dampening sheet and the backplate caused by shearing forces in the braking operation because of the conical shape of the protuberance.
In another prior brake pad assembly, as disclosed in German Patent 41 04 812, a dampening sheet is utilized with a recess that is coincident with a fastening recess formed in the backplate. A flange protrudes from the edge of the recess and is produced by lateral folding or beading of the dampening sheet. The flange may also consist of individual tongues. This arrangement again offers very little torsional resistance because the shearing forces, at least in part, always run in a direction in which they attempt to bend back the flange and in which the flange is not particularly strong.